Self-organisation is a process in which pattern at the global level of a system emerges solely from numerous interactions among the lower-level components of the system. Moreover, the rules specifying interactions among the system’s components are executed using only local information, without reference to the global pattern. In short, the pattern is an emergent property of the system rather than a property imposed on the system by an external ordering influence. [….] Emergent properties are features of a system that arise unexpectedly from interactions among the system’s components. An emergent property cannot be understood simply by examining in isolation the properties of the system’s components, but requires a consideration of the interactions among the system’s components. It is important to point out that system components do not necessarily have to interact directly. [….] Individuals may interact indirectly if the behaviour of one individual modifies the environment and thus affects the behaviour of other individuals.
Camazine S, Deneubourg J-L, Franks NR, Sneyd J, Theraulaz G, Bonabeau E (2003) Self-Organization in Biological Systems. Princeton University Press.